Method of producing etched intaglio printing-surfaces.



C. W. SAALBURG.

METHOD OF PRODUCING ETCHED INTAGLIO PRINTING SURFACES.

APPLICATION FILED FEB. 27. I9I7.

Patented Jan. 7, 1919.

LZQOFG,

UNITED sjrATEs PATENT OFFICE.

CHARLES W. SAALBURG, OF RICHMOND HILL, NEW YORK, ASSIGNOB T0 MULTIOOLOB INTAGLIO PRESS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

unrnon or rn'onucme n'rcnnn m'memo PRINTING-SURFACES.

To 1113 whom it may concern:

- .tion is to produce a durable etched printing surface and .also to obtain fine gradations of light and shade co ndent to the tions of light and shade. in the subjectmatter picture to be reproduced by use of photographically sensitized carbon tissue prints in a multicolor press printing operation.

'Another object of the invention is to produce a novel anddurable printing surface of the kind in question,'that is, of a combined half-tone and And another 0 ject is to produce a novel kind of press-printed etching having a plurality of colors some of which are superimposed, suc print or etching being characterized by a combined half-tone and grainscreen coloration.

In the accompanying drawings forming a part hereof and illustrating the principle of thisinvention in the best mode now known to me,-

Figure 1 is a face view of a half-tone positive.

Fig. 2 is a negative photographically-sensitized carbon-tissue or film print of the halftone positive shown in Fig. 1.

Fig. 3is aperspective view of an etchable roll, and shows the print which is shown in Fig. 2, transferred to and dried on the periphery of the roll.

Fig. 4 is a face view of a grain-screen photographically-sensitized carbon-tissue or film rmt. p Fig. 5 shows the grain screen film print shown in Fig. 4, transferred to and dried on the half-tone print film which is in place on the surface to be etched.

Referring to the drawings, the said halftone positive is indicated by 1 on any suit- Specification of Letters Patent.

- etching in-screen print structure.

Patented Jan. 7 1919.

Application filed February 27, 1917. Serial No. 151,169.

able transparent material. It shows as numerous dots 2 of various sizes, these dots showing in black in the drawings and defining the tones of the picture. This half-tonepositive I use for the purposes of the present method in assemblage with a sheet of photographically-sensitized carbon tissue or film to make the half-tone negative print 3 shown in Fig. 2, wherein the black dots 3 are the reverse of the black dots 2 shown in the positive 1. The black dots 3 in the negative film form a resist for the etching acld and consequently protect the underlying metal of an etchable surface from being attacked by the acid, and

walls of the ink-holding'recesses or pits 1n the etched surface; the white spaces 4 of the negative, between the dots 3, consituting film portions which are bitten through by the acid so that the acid eatsthrough the etchable metal to form the ink-holding recesses or pits. Not only is there undercutting, but also eating away of the top surfaces of the walls .when the half-tone dots are so small that the underlying metal is of minute area.

Now I find that I can overcome this serious objection and keep all the tones of the picture by superimposing a separate photographically-sensitized carbon tissue or film grain-screen print 6 of minute black grains or dots 7, the grain-screen black dots 7 being preferably near the size of the black dots of the negative. of the grain screen are acid resists and serve to enlarge the walls of the ink-holdin recesses finally formed in the parts 0 the metal where the thinnest walls would appear if the etching were made directly through the half-tone negative; and the combination of the half-tone and grain serves to give to the etching in the metal and the print made therefrom, a peculiarly harmonious and full tone picture of. a wholly distinctive character.

In Fig. 3 I show the half-tone film negative print transferred to and dried on an etchable roll 5.- Now the fact is that if the etching acid be applied directly to this negative the acid will undercut the walls of the cells and eat awayin whole or in part such walls, destroying the thinner walls first, es-

These black dots or grain 7 pecially in the blacks and three-quarter tones,-when and if the half-tone screen used is say from 85 to 17 5 lines to the inch, and it is this screen size which is required 5 in multicolor or monotone etched intaglio printing;- and it is assumed a screen of from 85 to 17 5 lines to the inch is used in the making of the negative tissue print. But whatever the number of screen lines per inch, the

the greater the liability to undercut theinkrecess walls.

Said grain screen print is indicated by 6. This grain-screen tissue or film print is transferred to and dried on the already dried half-tone negative print, making a double thickness of film through which to etch on the roll 5. 'The outer or grain screen tissue or film print constitutes 0.

screens or protects the image to be reproduced in the underlying half-tone negative from mutilation in the etching process, tends toprevent devils; and as a screening or protective print in connection with other kinds of film prints and other kinds of 7 screens, effects important novel advantages. My invention is not limited in respect to the prevention of devils to either the half-tone 80 negatives or to grain-screen prints referred to above, and the broad advantages of my duplex film method are as follows. The outer screening of protective film or tissue covers pinholes and blemishes in the under: lying image containing film print and prevents the acid from penetrating such'pinholes and blemishes, and obliterates devils arising from dust specks on the films, and.

prevents the acid from improperly attach-. ing the copper through them. Any such biting into the copper or etchable surface would produce ink-receiving recesses or cells where such' recesses were not wanted, and would result in blemishing the surface of the printed product. The pinholes, blemishes or devils are due to a variety of causes such as accidental perforations or bruises, to imperfections in manufacture, to dust specks, and to a considerable extent to inherent action during warm weather or under wrong-temperature and hygrometric conditions. In very warm weather or under otherwise adverse conditions, the devils and blemishes are particularly liable to be seen in large light-colored areas such as skies or flesh masses or the like, where the resultant imperfections are particularly objectionable. The screening or protective print if it has imperfections, can hardly be possibly placed on the underlying film print so that its entire imperfections will register with minute imperfections in the underlying print. While image-containing films are often printed with screens in glazed frames by ex- 66 posure to light, such an etchable medium law of the matter is that the finer the screen screening or protective print in that it;

the single film; and in applying the etching acid to such a film when it is in place on an 70 etchable surface, there is no adequate time and opportunity afforded to the etcher for the determination of the quality of his etch ing as the etchingproceeds, and very often a the etching under such conditions has to be 5 stopped before completion, by reason of such imperfections. In such case the etcher has no recourse except to start his work over again or to produce an undesirablev etched printing surface. By my invention of the duplex films as stated, because the subject-matter image to be-reproduced is underneath the screening or protective tissue I print or film and protected thereby, the etcher has much more timeand opportunity for .observation of the effects of the acid and ,ofthe quality'of the etching which is being desired effects on paper and fabrics generally, but also in the printing of some classes of textile fabrics for forcing the inkclear through the goods and so securing the required printed appearance of some classes of goods on the so-called wrong side thereof. There is a most important physical effect produced by the described duplex process, and it lies in the fact that the screening print, while resulting in the two marked advantages above stated, does not permit, but prevents, mutilation of the image embodied in the under tissue or film. The outer print is bitten through without the acid reaching the image-containing portion of the composite or duplex film structure; whereas, if the positions of the two films were reversed, then the acid would operate in the image- 115 containing film which would be outermost and bite it variously before coming to the under film with its dot or stipple or other shade-forming images, -and the resultant etching would be blurry where by the present process it is strong, sharp and clear.

Whether the positive and the carbon-tissue or film print of' the positive are halftone or not, and whether the screen print is a grain screen print or not, the duplex film process described possesses a peculiar advantage which in some classes of work is particularly intensified -by using the described half-tone positive half-tone film print and grain screen print in producing color originals, I may employ photographiccolor-separation processes or the like. In any event the etched printing surface and the printed'etching in multlcolor possess striking increased sharpness and degrees of tone shades. The, acid bites through the unexposed white 'dots '0I equivalents of the protective screen print first, and consequently the thinnest parts of the underlying image-containing film are attacked before its other parts are attacked, and then the acid spreads and bites on and into the underlying image-containing according to the varying thicknesses thereof. It will be understood that each of the films has its .usual paper back stripped off. The screening or protective print being outermost, insures the production of all the shades or shading in theneg'ative film by reason of the latter being fortified by the outward protecting screen.

' In addition to its utility as ascreening or protective film print, the print which contains the image to be reproduced in etching the printing surface and subsequently to be reproduced on the product which is pressprinted from the etched roll when combined with an overlying fine grain screen, is of great practical importance in the following important particulars: The grain of the grain screen which, according to the present invention, is also: a screening orprotective screen as above referred to, efi'ects marked' strength and durability of the tooth of the metal etching, that is of the metal surrounding the ink-holding cavities, cells, or pits made in the surface of the roll or of a plate by the etching acid; and this durability of tooth is of very great'importance, first in prolonging the life of the tooth under the action of the doctor blade of the press and the general wear due to its use in making printed impressions, and secondly bythe maintenance. of the tooth in securing a non-blurred printing effect especially in the printing of long editions where a blurring efi'ect obtains as soon as the tooth of 'a plate wears. Of course the finer tooth wears down more quickly than the coarser tooth, and as the fine tooth corresponds to the darker shaded spaces of intaglio printed products any wearing down -of these finer teeth results in a blurred black or other color or in other more or less blurred or solid ink surfaces in the product where only a fine shading of the color is desired. By the grain screen feature of the present invention the grain effected by the grain screen of uniform sized dots, fills in or covers the portions of the'underlying negative half-tone film where the dots are very fine and would etch away or beliable to be etched away if they were not, protected by the screen or protective fine screen print unless great care were exercised by the etcher n the application of the acid, as occurs in the etching of ordinary half-tone positive films.

Such covering or filling in of the halftone negative with its dots of varying sizes by a fine screen film or tissue print which forms an overlying screening or protective screening print having dots of substantially uniform size and closely assembled together prevents the acid from attacking the finer dots of the half-tone and insures a durable tooth in the etched printing surface, and also a sharply defined intaglio printed product.

The importance of this invention in connection with the half-tone positive, the negative film print made therefrom, and the grain screen print method, may be further explained as follows. A half-tone picture,

is composed of small dots of varying sizes the ink, and the ultimate result is that the paper on which the press printing is done becomes smudged. Therefore in order to prevent such a smudge I use the protective film print6 comprising a series of fine grain dots which automatically under the etching action of theacid will produce proper inkreceiving wells in the dots, giving the wells or pits suitable mechanical strength for practical use in press printing. The grain film where the grain does not exist forms a protection for the underlying half-tone small dots, and this outward grain film effects a toothing of the met-a1 which toothing would be greatly impaired or destroyed if it were accomplished by use of the halftion, would destroy the under structure of the positive film print. But whether the under film print 3 is a half-tone or a flowing gelatin print, the superimposed outer screen print advantageously afiects the mechanical strutcure of the etching on the printing member, and enhances the beautyof theultimate multicolor intaglio print.

What I claim is,'

1. The process of avoiding devils consisting in transferring to an etchable roll or plate a carbon negative print film containing the image of subject-matter to be reproduced and drying such film on the etchable surface; and in thereafter transferring to and dry n' on such image-containing film, a sensit zed carbon-tissue screening film print; and in subjecting the superimposed films and such parts of the etchable roll 'or plate as are to be etched, to a suitable etching acid.

2. The method of making etched printing rolls or surfaces for, printing, conslstin in transferring a photographically-sensit1zed carbon-tissue print of a subject-matter image to be reproduced and made from an isochromatic negative to an etchable surface; in drying such print in place on such surface; in transferring to such. dried image-containing print a photogr'aphicallysensitized carbon-tissue print of screen, dot, stip-ple or-fother shading character and drying such protecting or screening print thereon; and in applying to such film assemblage an etching acid.

3. The method of making modified halft'one etchings on an etchable surface to be used in printing, consisting in transferring a photographic'ally-sensitized carbon-tissue half-tone negative print to said surfaceand allowing it to dry in place; in superimposing over such dried negative print a photographically-sensitized carbon-tissue grainscreen print and allowing it to dry on the underl ying-hal-f-tone negative tissue print; and in acid-etching through such superimposed tissue prints. v 1

4. As a new article of manufacture, a superimposed-color, multi-color etched print, the coloration whereof comprises combined half-tone and grain screen coloration i'mpressions.

In testimony whereof I have hereunto set my hand this 24th day of February, 1917.

CHARLES W. SAALBURG. 

